Using clang-format on Chromium C++ Code

Easiest usage, from the command line

To automatically format a pending patch according to Chromium style, from the command line, simply run: git cl format This should work on all platforms (yes, even Windows) without any set up or configuration: the tool comes with your checkout. Like other git-cl commands, this operates on a diff relative to the upstream branch. Only the lines that you've already touched in your patch will be reformatted. You can commit your changes to your git branch and then run git cl format, after which git diff will show you what clang-format changed. Alternatively, you can run git cl format with your changes uncommitted, and then commit your now-formatted code.

Editor integrations

Many developers find it useful to integrate the clang-format tool with their editor of choice. As a convenience, the scripts for this are also available in your checkout of Chrome under src/buildtools/clang_format/script/.

If you use an editor integration, you should try to make sure that you‘re using the version of clang-format that comes with your checkout. That way, you’ll automatically get updates and be running a tool that formats consistently with other developers. The binary lives under src/buildtools, but it‘s also in your path indirectly via a depot_tools launcher script: clang-format (clang-format.bat on Windows). Assuming that depot_tools is in your editor’s PATH and the editor command runs from a working directory inside the Chromium checkout, the editor scripts (which anticipate clang-format on the path) should work.

For vim, :so tools/vim/clang-format.vim and then hit cmd-shift-i (mac) ctrl-shift-i (elsewhere) to indent the current line or current selection.

Are robots taking over my freedom to choose where newlines go?

No. For the project as a whole, using clang-format is just one optional way to format your code. While it will produce style-guide conformant code, other formattings would also satisfy the style guide, and all are okay.

Having said that, many clang-format converts have found that relying on a tool saves both them and their reviewers time. The saved time can then be used to discover functional defects in their patch, to address style/readability concerns whose resolution can't be automated, or to do something else that matters.

In directories where most contributors have already adopted clang-format, and code is already consistent with what clang-format would produce, some teams intend to experiment with standardizing on clang-format. When these local standards apply, it will be enforced by a PRESUBMIT.py check.